1. Field of the Invention
The present invention relates to a method of fabricating a liquid crystal display device, and more particularly, to a method of forming color filters on a substrate of the liquid crystal display.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) of an active matrix driving system uses thin film transistors (TFT""s) as switching devices to display a moving picture. Since such an LCD can be made smaller in size than the existing cathode ray tube (CRT) it has been widely used for a monitor for a personal computer or a notebook computer as well as an office automation equipment (e.g., a copy machine) and a portable device (e.g., a cellular phone or a pager).
A process of fabricating such an active matrix LCD includes substrate cleaning, substrate manufacturing, substrate adhesion/liquid crystal injection and packaging steps. The substrate manufacturing step is divided into manufacturing a color filter substrate and manufacturing a thin film transistor substrate.
FIGS. 1A to FIG. 1D illustrate a conventional method of manufacturing a color filter substrate. Referring to FIGS. 1A to 1D, the conventional color filter substrate manufacturing method includes forming a black matrix 8 on an upper substrate 10, forming red (R), green (G) and blue (B) color filters 2, 4, and 6, forming a common electrode 12, and forming an alignment film 14. The black matrix 8 is formed on the upper substrate 10, as shown in FIG. 1A, to prevent an optical interference among the adjacent red, green, and blue color filters 2, 4, and 6. The black matrix 8 is positioned at each boundary portion of the color filters 2, 4, and 6, as shown in FIG. 1B. Such color filters 2, 4, and 6 transmit light having a specific wavelength band to display red, green, and blue colors. The common electrode 12 is entirely deposited on the color filters 2, 4, and 6, as shown in FIG. 1C. The alignment film 14 is entirely formed on the common electrode 12, as shown in FIG. 1D. The alignment film 14 is usually made from polyimide.
However, the conventional color filter substrate manufacturing method has a problem in that a domain defect differentiating an alignment direction of a liquid crystal is generated at an alignment film 14 formed on the boundary portion between the color filters 2, 4, and 6. This is due to a step coverage between the black matrix 8 and the color filter 2, 4, or 6. More specifically, if a slope of the step coverage of the color filter is close to 90xc2x0, the alignment film 14 has a concave shape at the black matrix portion. Also, a rubbing problem results, as shown in FIGS. 2A and 2B. In other words, in the course of the rubbing process, liquid crystal molecules positioned at the step coverage of the color filter become aligned in a direction different from an alignment direction of most liquid crystal molecules. As a result, a domain defect (i.e., reverse tilt) is generated at a place corresponding to the step coverage of the color filter on the substrate consisting of a plurality of pixel cells 22 as shown in FIG. 3.
Accordingly, the present invention is directed to a method of fabricating a liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is a method of fabricating a liquid crystal display, wherein a slope of a step coverage of a color filter is reduced so as to prevent rubbing problems.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method of fabricating a liquid crystal display device includes forming color filters on an upper substrate such that a slope of a step coverage existing at each boundary portion between the color filters is less than a desired angle; and forming an alignment film on the color filters.
In another aspect of the present invention, a method of fabricating a liquid crystal display device comprises forming a black matrix on a first substrate; forming a color resist on the first substrate and the black matrix; forming an oxygen shielding film on the color resist; forming first, second and third color filters each having at least one side portion having a slope of about 20 degrees or less; and forming a common electrode over the color filters.
In another aspect of the present invention, a method of fabricating a liquid crystal display device comprises forming a black matrix on a first substrate; forming a color resist on the first substrate and the black matrix; forming an oxygen shielding film on the color resist; forming red, green and blue color filters each having at least one side portion having a slope of about 20 degrees or less, the color filters being formed by curing portions of the color resist with an ultraviolet ray using a photomask, wherein the slope of the one side portion of the first color filter ends at a first position on the black matrix and the slope of the one side portion of the second color filter ends at a second position on the black matrix, the first position being spaced from the second position; forming a common electrode over the color filters; and forming an alignment layer on the substrate.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.